This invention relates to a novel piston construction and more particularly to the combination of such piston construction with means for effectively sealing the same against leakage between the piston and the cylinder in which it operates.
It is known in the prior art to provide piston means with an expansible ring or rings for sealing the piston against fluid leakage in conjunction with bearing rings which encircle the piston and have axial sliding engagement with the interior wall of the cylinder in which the piston operates. Examples of constructions of this general type are found in my prior U.S. Pat. No. 3,588,134 dated June 28, 1971 and U.S. Pat. No. 3,885,800 dated May 27, 1975.
As shown in the former of the above two patents the bearing ring may comprise a composite structure including an aluminum supporting ring having an encircling ring of synthetic plastic material, for instance nylon, which directly engages the cylinder wall to provide a bearing of relatively low frictional characteristics.